1. Technical Field
The present invention concerns a method for inserting and fixing a mounting insert with a recessing section by means of an adhesive bonding technique into a lightweight sandwich panel comprising a core layer and two cover layers that are attached to the opposing main surfaces of the core layer. Moreover, the application concerns a mounting insert for installation into a lightweight sandwich panel.
2. Background Information
It is known per se to use lightweight sandwich panels for lining applications, for building furniture and other similar tasks. This technology is used especially in applications where saving weight is of great interest, particularly in the construction of aircraft for the building of interior furnishings and the lining of aircraft, but also in the boat building industry for fitting out boats and ships. In these instances the use of lightweight sandwich panels excels particularly since they are low in weight through the use of lightweight core layers or core panels respectively, which often come in a honeycomb structure, but through the particular construction of said core layer or core panel respectively and the firm connection with the cover panels they still provide sufficient strength to be able to make sufficiently robust and durable or strong installations, for example furnishings or lining.
To be able to combine more complex shapes made from such lightweight sandwich panels, for example furniture such as cabinets or shelving, the panels must be connected to each other in many different ways. To achieve this, mounting inserts are inserted into the lightweight sandwich panels, which are often provided with internal threads into which matching screws are fixed that are connected to another lightweight sandwich panel or another component.
Such mounting inserts are often designed in the form of a sleeve, or they have an internal thread in the form of a blind hole. To insert and fix these mounting inserts in the lightweight sandwich panels, corresponding recesses are provided in the lightweight sandwich panel, the mounting inserts are inserted and fixed with an adhesive. Examples for this are provided in documents DE-OS 14 00 888, DE 14 00 886 A and DE 28 34 237 B1.
The methods for inserting and fixing a mounting insert, using the methods described in said documents, have in common that a borehole is formed in a lightweight sandwich panel, where said borehole passes through the cover layer and into a core layer, which in the examples described is in the form of a honeycomb structure. The mounting insert is placed into said borehole. The mounting insert is adhesively bonded in that the entire space of the borehole that surrounds the mounting insert is filled with an adhesive or a casting resin respectively, which, in the sense of the invention, also constitutes an adhesive. In the method known per se, said adhesive also penetrates in part into the existing honeycomb structure and is able to flow up to the opposite cover layer.
Although the known methods achieve the aim of securely fixing the mounting insert in the lightweight sandwich panel, problems are observed with mounting inserts that are fixed according to the known methods, and with the lightweight sandwich panels that are fitted with said mounting inserts, the cause of which has not been found so far, nor has the problem been solved in a satisfactory manner.
When a fastener is engaged in such a mounting insert, for example a screw is inserted into the internal thread of such a mounting insert for the purpose of, for example, fastening two lightweight sandwich panels to each other, a tensile force is applied via said screw in the direction of the cover layer through which the mounting insert is inserted, and an indentation appears on the side opposite to that side of the lightweight sandwich panel into which the fastener, e.g., the screw, was inserted, thus causing a concave dent in the opposite cover layer in the vicinity of the mounting insert. Said dents are visually detracting, particularly in areas where the respective lightweight sandwich panel is exposed. To correct these defects, the dents that have formed are still manually reworked in a time-consuming manner in that a transparent or colored paint is applied to fill said dents, thus retouching them. This manual rework is not only elaborate and costly, the retouching of the defects is usually insufficient and the faults are not completely corrected.